In manufacturing articles, such as automobiles, household appliances and industrial machines, a metal and a resin often need to be firmly bonded together. In conventional methods, an adhesive may be used at normal temperature or under heating to integrally bond a metal and a synthetic resin. Alternatively, a resin may be bonded to a magnesium alloy, an aluminum alloy, or ferroalloys such as stainless steel directly without an adhesive.
Nano molding technology (NMT) is a technique of integrally bonding a metal and a resin, and allows the resin to be directly injection molded on a surface of a metal sheet by nano molding the surface of the metal sheet so as to obtain a metal-resin integrally molded product. For effective bonding of a metal and a resin, NMT may replace commonly used insert molding or zinc-aluminum or magnesium-aluminum die casting so as to provide a metal-resin integrally molded product with low cost and high performance. Compared with other bonding technologies, NMT may reduce the weight of the final product, may ensure excellent strength of the mechanical structure, high processing rate, high output, and allows more appearance decoration methods, consequently applicable to vehicles, IT equipment, and 3C products.
Japan Taisei Plas Co., Ltd. filed a series of patent applications, for example, CN1492804A, CN1717323A, CN101341023A and CN101631671A, which propose a method for integrally molding a metal and a resin composition. In this method, by using a resin composition containing polyphenylene sulfide (PPS), polybutylene terephthalate (PBT) and polyamide (PA) with high crystallinity as an injection molding material, the resin composition is directly injection molded on a surface of a nano molded aluminum alloy layer to allow the resin composition to immerse in a nanoscale micropore (i.e., nanopore), so as to obtain a metal-resin integrally molded product with a certain mechanical strength. However, because the resins used in this method are all highly crystalline resins, the molding process requries a longer cooling time and a narrow range of mold temperature in the course of molding to ensure modeling performance. In addition, the highly crystalline resins often make the plastic surface hard to process, resulting in significant variations of the appearance among the finish products.